You can't always know with every fragrance. Buying full bottles is really a personal choice. Many people here only buy decants or smallest bottles available, unless it's a fragrance they really love and have been wearing for a long time.
Personally I don't mind having full bottles of perfumes I no longer enjoy, I can always let a friend use them, or maybe I'll come back to them later. If you can't do that, or don't want to waste your money, then just buy decants or the smallest bottle available.
Oh and in general, of all types of fragrances, sweet fragrances can get really cloying or disgusting if you have a bad experience with them, so it's not uncommon at all. In fact I've only had such an experience with sweet -highly synthetic- fragrances.